1. Field of the Invention
This invention relates generally to a system and method for detecting whether a vehicle driver is holding a steering wheel of the vehicle and, more particularly, to a system and method for determining whether a vehicle driver is holding a steering wheel of the vehicle when the vehicle is in an autonomous, semi-autonomous or manual driving mode by measuring steering torque and steering angle, and using both steering torque and resonant frequency of steering oscillation to determine whether the driver is holding the steering wheel.
2. Description of the Related Art
The automobile industry has been making continuous efforts to enhance the comfort and safety of the occupants of a vehicle, especially the driver. These endeavors have resulted in various technologies, such as advanced driver assistance systems (ADAS) and electronic stability control (ESC) systems. Some of the types of ADAS are adaptive cruise control systems, lane keeping assist systems and lane centering control steering systems. ESC systems, on the other hand, use computerized technologies that improve vehicle handling by detecting and preventing unstable conditions.
Another type of ADAS is an active front steering (AFS) system that adds or subtracts a steering component to the angular movement of the steering wheel in order to reduce the driver effort required to rotate the steering wheel and/or augment the driver steering for improved vehicle safety and stability. The resulting steering angle thus includes the steering input by the driver and the component contributed by the steering system.
The operation of modern vehicles is further becoming more autonomous, i.e., vehicles are able to provide driving control with less driver intervention. Cruise control systems have been on vehicles for a number of years where the vehicle operator can set a particular speed of the vehicle, and the vehicle will maintain that speed without the driver operating the throttle. Adaptive cruise control systems have been recently developed where not only does the system maintain the set speed, but it also will automatically slow the vehicle down in the event that a slower-moving preceding vehicle is detected using various sensors, such as radar and cameras. Certain modern vehicles also provide semi-autonomous parking, where the vehicle will automatically provide the steering control for parking the vehicle. Some vehicle systems intervene if the driver makes harsh steering changes that may affect vehicle stability, while others are designed to maintain the vehicle within a lane or near the center of a lane on the road. Further, fully autonomous vehicles have been demonstrated that can drive in simulated urban traffic up to 30 mph, observing all of the rules of the road.
The systems described above aid the driver by reducing the driving burden. However, it is typically not desirable to reduce the driver's vigilance and attentiveness, even when such systems are providing some or most of the control of the vehicle. It is generally required that the driver keeps his/her hands on the steering wheel, and is ready to take over the steering control whenever the situation demands. Quick and reliable determination of whether the driver's hands are on the steering wheel is needed, whether in a manual steering mode or a system-assisted steering mode.